On the possibility of severe corrosion of a Ni-W-Cr alloy in fluoride molten salts at high temperature

•Ni-26W-6Cr alloy shows a good corrosion resistance to FLiNaK salts at 800 °C.•W and Mo have the similar immunities to salts and lower diffusion rates than Cr.•Cr diffuses outwardly into salts and Cr-depletion layer form in the alloy surface.•W and Mo have little effects on the diffusion of Cr in Ni-based alloys.